1. Field of the Invention
Generally, the field of the present invention is adhesion bonding with semiconductors. More particularly, the present invention relates to the adhesion of metallic layers to p-type III-V compound semiconductors.
2. Background Art
In order to enhance the performance of semiconductors, advances have been made in types of materials used and methods for forming those materials. One such area of performance pertains to the formation and structure of metal and semiconductor contact. For semiconductor lasers, this contact should be ohmic, that is, the contact should exhibit linear I-V characteristics, and a low contact resistance is required. U.S. Pat. No. 5,429,986 describes a process for forming a low resistance ohmic contact electrode that has a layer of Pt interposed between a p-type GaAs layer and a Ti/Pt/Au layer wherein the interposed Pt layer has a thickness greater than 50 Å and less than 400 Å. The '986 also extrapolates that for thicknesses less than 50 Å, unsuitable contact resistances are obtained.
However, in addition to contact resistance, other characteristics are desirable for contacts formed on p-type semiconductors. For example, the time required to complete the formation of a contact through annealing can impact the overall cost of manufacturing devices utilizing the contacts. Additionally, the adhesion strength between contact metals and underlying semiconductor and insulating layers can allow subsequent fabrication steps without metal peeling and can determine the infant mortality rate and useful life of devices incorporating the contacts. Thus, reliability remains important and concomitant attributes such as robustness and versatility can extend the scope of use of products fabricated with ohmic contacts.
Thus, despite the considerable efforts that have been exerted for many years, there remains a long felt need for a p-metal that provides superior strength, reliability, and processing time without any attendant drawbacks.